1. Field of the Invention
The invention relates to a process for the production of phenolic resin foam plastics wherein an alkaline-condensed phenol-formaldehyde resin is mixed with an expanding agent and an acidic curing agent after which the said mixture is subjected to foaming and permitted to cure.
2. Description of the Prior Art
As is known, phenolic resin foam plastics burn when exposed to an open flame. In order to eliminate this major disadvantage various flame-retarding agents and substances are added to phenolic resin foam plastics to render them flame-resistant. Thus, German Offenlegungsschrift No. 1,669,833 recommends the addition of copolymers from silicones and glycol. Other well-known fire-retarding agents for phenolic resin foam plastics are nitrogen-containing compounds, such as urea, melamine and dicyandiamide.
In German Offenlegungsschrift No. 1,923,719 it is recommended to use such nitrogen-containing substances not in admixtures with the phenolic resin but in combination with the acidic catalyst. The nitrogen-containing compound is employed to form, with the acidic catalyst, an addition compound remaining stable in the acid medium.
The disadvantage of the conventional flame-resistance or flame-retarding phenolic resin foam plastics is that, compared to foam plastics of the same composition not containing the flame-retarding agent, they are mechanically less stable.
It is the object of this invention to provide a process permitting the production of phenolic resin foam plastics having outstanding flame-resistance and, at the same time, having the good mechanical stability typical for phenolic resin hard foam plastics.